Exercise normally causes activation of a portion of the body's reflex nervous system called the 'sympathetic' nervous system, which results in increased heart rate and blood pressure. The mechanisms by which exercise increases sympathetic nervous system activity is unclear. This research is designed to examine whether sympathetic nervous system activation alters the ability of muscle to exercise. This study will use the local forearm infusion of an FDA approved drug called Bretylium to temporarily block the release of the chemical norepinephrine. This technique used previously by other researchers is called a Bretylium "Bier Block".